# converting digital signals to analog

I'm trying to take 12 digital signals and convert them to a linear analog signal (0-10 V or 0-20 mA). In an ideal world each digital signal would increase the analog output by 0.83 V and it wouldn't matter what order the digital inputs are on. So if I had bit 0 and 11 on I would get 1.66 V or if bit 3 and 4 are on I would get the same.

Is this possible with a DAC or R2R ladder?

Thanks

• Not with a "normal" DAC or an R2R as these are binary weighted already. Think about a resistor string but without the weighting, and you'll get somewhere... – awjlogan May 9 '18 at 11:06
• yea.....circuit diagram is all over google – Mitu Raj May 9 '18 at 11:07

## 1 Answer

Feed all 12 signals via equal value resistors into a summing node of an op-amp like this: - But remember this is an inverting summing circuit so you'll need another op-amp inverter on the output to convert from negative voltages to positive ones.

Just four inputs are shown for clarity with R1=R2=R3=R4. Make them all 10k for instance. Rf then is used to set the gain. If V1 is 5 volts and you need -0.83 volts on the output then Rf is 1660 ohms but don't forget to invert this back to +0.83 volts.

Compare the above with a circuit that is more conventionally regarded as a proper DAC. It uses weighted resistor values on each digital input: - 